Preheat oven to 400 degrees. Let pie shell stand at room temperature for 10 minutes. Bake 7 minutes. Remove from oven.
Put oil in frying pan. Saute onion and mushrooms. Place cheese in pie shell. Pour onion and mushrooms on top of cheese.
In a bowl combine eggs, milk, salt and pepper. Beat with fork until well mixed. Pour egg mixture over onions and cheese. Sprinkle with paprika. Bake 45 minutes or until inserted toothpick comes out clean. Top with sour cream.
Variations: Use dried fried onions in place of regular onions. Use half in the quiche and the other half to top over egg mixture before baking.
